Field of the Invention
The present invention relates to a VR resolver (Variable Reluctance resolver) that may be used for measuring a rotation angle of a motor.
Description of Related Art
In general, VR resolvers are formed primarily of a ring-like stator and a rotor that is arranged inside the stator. The stator has a ring-like stator core, a first insulator and a second insulator that have electric insulating characteristics, and coils. The stator core is formed by laminating plural circular yoke sheet members that are obtained by press cutting soft magnetic materials. The stator core is held between the first insulator and the second insulator from both end surfaces of the stator core. The stator core is formed with plural salient poles at an inner circumferential surface thereof, and the coils are wound to the salient poles via the first insulator and the second insulator.
Such a resolver may be inserted and mounted in a tubular case together with a device to be measured, such as a motor or the like. In this case, the resolver must be fixed in the case, and therefore, the resolver must be provided with a screw hole or the like at the outer circumferential surface thereof for fixing. In this fixing method, space is necessary at the outer circumference of the main body of the resolver for the fixing. However, there may be cases in which the space cannot be provided when the resolver is mounted in a limited space such as in an automobile. In this regard, a structure, in which a main body of a resolver and a housing for fixing are integrally formed, is disclosed in, for example, Japanese Unexamined Patent Application Laid-open No. 2008-164534.
According to the invention disclosed in Japanese Unexamined Patent Application Laid-open No. 2008-164534, a housing, an insulator for electric insulating, and a terminal base portion are integrally formed by using a stator core and a terminal block as cores for insert molding, and then wires are wound. Thus, the main body of the resolver and the housing are integrally formed. When a resolver and a device to be measured are inserted and mounted in a tubular case, the outer shape of the housing must correspond with the outer shape of the case. In the invention disclosed in Japanese Unexamined Patent Application Laid-open No. 2008-164534, the mold is complicated so as to insert mold the stator core and the terminal block. Therefore, the housing function cannot be provided in the vicinity of the terminal base portion that is a connection to the outside. Moreover, cooling rate of resin varies due to the insert molding of the metals of the stator core and the terminal block, whereby dimensional accuracy is degraded, which may cause difficulties in matching the axes of the resolver and a device in assembly.